Editing Java Native Interface (section)

== Performance ==
JNI incurs considerable overhead and performance loss under certain circumstances:<ref name="StackOverflow: What makes JNI calls slow?">{{cite web|url=https://stackoverflow.com/a/7809300/1068537|title=Java: What makes JNI calls slow? |website=Stack Overflow}}</ref>
* Function calls to JNI methods are expensive, especially when calling a method repeatedly.
* Native methods are not inlined by the JVM, nor can the method be [[Just-in-time compilation|JIT compiled]], as the method is already compiled.
* A Java array may be copied for access in native code, and later copied back. The cost can be linear in the size of the array.
* If the method is passed an object, or needs to make a callback, then the native method will likely be making its own calls to the JVM. Accessing Java fields, methods and types from the native code requires something similar to [[reflective programming]] (reflection). Signatures are specified in strings and queried from the JVM. This is both slow and error-prone.
* Java Strings are objects, have length and are encoded. Accessing or creating a string may require an O(n) copy.